The present invention relates generally to security sensors and to energy-conservative sensors for sensing entry into a monitored area or room. More specifically, the present invention relates to passive sensors for automatically lighting and extinguishing lights when a person enters and leaves a room.
Passive infared (PIR) motion sensing is an expanding technology driven by security and energy conservation demands. One typical use of conventional PIR technology is automatic illumination of room lighting when a person enters a room. A timer will automatically extinguish the lights after a predetermined interval unless the PIR detects the person moving in the room. A disadvantage of these motion-only sensors is that the sensor may not detect a presence of person out of a line-of-sight of the PIR but still within the room. In this case, the sensor extinguishes the lights while the person remains in the room. The consequences of this premature loss of light range from inconvenience and annoyance to potential hazard and bodily injury, depending upon the particular room or area monitored. In some instances, a person may merely have to wave or stand to trigger the sensor while in other instances the person way have to move to a monitored part of the room in darkness.
These prior art room sensors typically employ the same mechanism for triggering and retriggering. That is, the sensor will illuminate room lights (trigger them) when it detects motion and will reset a timer (retrigger the lights) when it detects motion.